Catalases of Aspergillus fumigatus and Inflammation in Aspergillosis

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The article describs various features of aspergillosis and a discussed the role of calatases produced by <i>Aspergillus fumigatus</i> during infection. Since a large body of invasive <i>Aspergillus</i> infection occurs as an opportunistic infection in variously impaired defense mechanisms, there is a wide spectrum of histopathological features of lesions demonstrated at the site of infection. Accordingly, histopathology of the lesions can be understood as a phenotypical representation of interaction between differently impaired functions of neutrophils and macrophages and virulence factors of invading <i>Aspergilli</i>. Consideration of previous pathological knowledge regarding infection and inflammation provides much important information to predict the pathophysiology of a patient. Meanwhile, detoxification of hydrogen peroxide by catalases has been proposed as a way to overcome this host response. <i>A. fumigatus</i> produces three active catalases, one from conidia and two from mycelia. CatAp, a spore specific monofunctional catalase, is resistant to heat and metal ions. In spite of their increased sensitivity to H<sub>2</sub>O<sub>2</sub>, killing of <i>catA</i> conidia by alveolar macrophages, virulence in animals was similar to wild type conidia. In contrast to mycelial Cat1p, and CatAp catalases, the mycelial Cat2p is a bifunctional catalase-peroxidase enzyme and is also sensitive to heat, metal ions and detergent. Surprisingly, the mycelium of the double <i>cat1 cat2</i> mutant with no catalase activity has only a slightly increased sensitivity to H<sub>2</sub>O<sub>2</sub> and was as sensitive to the killing of polymorphonuclear neutrophils as the wild type strain. However, it showed a delayed infection in the rat model of aspergillosis compared to the wild type strain. Consequently, it should be emphasized that conidial catalase is not a virulence factor but that mycelial catalases transiently protect the fungus from the host defence reactions.


  • Japanese Journal of Medical Mycology  

    Japanese Journal of Medical Mycology 47(4), 249-255, 2006-10-31 

    The Japanese Society for Medical Mycology

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